This invention relates generally to electronic timepieces having an electro-optic digital time display, and more particularly to a switching mechanism for selectively activating a display to provide illuminated readings of hours and minutes, seconds or calendar date.
Battery-operated electronic timepieces are known which make use of a quartz-crystal high-frequency oscillator as a frequency standard, the frequency of the standard being divided down by a frequency converter to produce pulses for activating the elements of an electro-optic digital time display.
In U.S. Pat. Nos. 3,560,998, 3,576,099 and 3,664,118 among others, there is disclosed wrist watches of the type in which the optical display takes the form of light-emitting diodes (LED's) which present the hours, minutes and seconds of time in digital decimal form and which are energized, on demand, at the option of the wearer. Since the display is normally de-energized and invisible, this assures minimum power consumption and an increasingly long life for the watch battery. The electronic circuits employed in commercial versions of such timepieces are in integrated circuit form to provide a highly compact structure.
Modules are currently available which combine the integrated circuit of the electronic timepiece with an LED time display, thereby greatly simplifying manufacturing procedures, for all that is necessary to assemble a watch is to encase the module and to provide the necessary switch connections for activating and setting the LED display. In one such commercially available quartz-crystal digital watch module manufactured by the Microelectronic Products Division of the Hughes Aircraft Company, a four digit LED display is included to afford readings of hours and minutes, seconds or calendar date.
All four digits are required for an hours and minutes or time-of-day reading, such as 12:25, whereas since a seconds reading is in a scale from 1 to 60, only two of the digits are needed. And since the scale for the calendar date has a maximum of 31, this reading only requires two of the four digits.
In the Hughes module, as incorporated for example in the Elgin "Minicon" watch described in the instruction book published (9-15-73) by Elgin Watch Company of New York City, three exposed contact terminals are provided on the module, the terminals operating in conjunction with two push-button switches on the watch case to selectively activate the digital read-out by means of a suitable logic circuit. We shall identify these switches as A and B. The first exposed contact terminals is the ground terminal and is connected to the case. When switch A is pressed in, it serves to connect the second terminal to the case and hence to the grounded terminal, the logic circuit arrangement being such that the time of day is then activated and displayed. When switch B is pressed, it serves to connect the third contact terminal to ground, the circuit arrangement being such that the display is then the calendar date. And when buttons A and B are pressed simultaneously, only the "seconds" is displayed.
There is also a fourth terminal acting in conjunction with a third switching button C which, when pressed, will cause whatever reading is being presented by operation of buttons A and B to advance rapidly, thereby to set the display. For example, if when button A is pressed, the display reads 12:25, then by also pressing the setting button C, the reading will advance in rapid steps to 12:26, 12:27 etc., the setting button being held in until the reading is at the desired setting, at which point button C is released. But since in the present invention, the setting mechanism is unchanged, no further consideration will be given to the fourth terminal and its associated switch button.
From the electrical and mechanical standpoint, there is nothing objectionable in a two-button switching system for selectively activating the digital read-out, but in terms of human engineeing, it has practical drawbacks. The wearer of the watch must not only manipulate two buttons, but he must also bear in mind which of the two buttons activates which display, and when it becomes necessary to press both buttons simultaneously. One cannot, as a practical matter, in a watch, label the two buttons, nor can one so distinctly locate these two buttons as to avoid improper action.
The same Hughes module may be incorporated in a pendant or pocket watch. In its traditional mechanical movement form, a pocket or pendant watch has a crown and stem arrangement for winding and setting purposes. The presence of switch buttons in an electronic version of a pendant or pocket watch is incongruous for it violates the traditional appearance of this watch form, and it is further objectionable for the reasons given above in connection with wrist watches.